Диагностика частотной области изоляции трансформатора

The first part of paper deals with the base information about diagnostics of power transformers. In this part are presented differently insulating methods, for example method of recovery voltage method, method of polarization and depolarization currents and chromatographic analysis. The second part of paper deals use of method of frequency domain spectroscopy for oil power transformers. This method is used in analysis insulating condition of power transformer with system of oil-paper. It was found, that the results of these tests are highly impacted by the operating temperature during the experimental measurement. Moisture and conductivity between insulating paper and oil in an insulating system are highly dependent from temperature. In the other part, the paper presents experimental results of the frequency diagnostic measurement for a real single-phase traction transformer 110/27 kV at different operating temperatures and states (with oil and without). Finally in the last part, the paper presents comparing frequency insulating measurements among several the same single-phase transformers 110/27 kV

Equivalent Circuits for FeCoZr-Al2O3 Nanocomposite Films Deposited in Argon and Argon-Oxygen Atmospheres

The investigation of the equivalent circuits for granular nanocomposite films was performed according to the method of the impedance spectroscopy. The films, consisted of the Fe0.45Co0.45Zr0.10 ferromagnetic alloy nanoparticles embedded into amorphous dielectric alumina matrix, were deposited in pure argon or argon and oxygen mixture. The temperature dependences of active and reactive components in the equivalent circuits for the (Fe0.45Co0.45Zr0.10)x(Al2O3)(1-x) nanocomposite films are compared and analyzed. The presence of the inductive part in the equivalent circuits for the samples deposited in Ar gas below and beyond percolation threshold is shown. It is revealed that the equivalent circuits of the (Fe0.45Co0.45Zr0.10)x(Al2O3)(1-x) nanocomposites produced in argon + oxygen gas mixture show more strong inductive contribution than ones sputtered in pure argon

Magnetotransport in Nanostructured Ni Films Electrodeposited on Si Substrate

The study of electrical resistivity  and magnetoresistance MR in nanogranular Ni films was performed over the temperature range 2 - 300 K and at the magnetic field induction B up to 8 T. The Ni layers having a thickness of about 500 nm were prepared by electrodeposition on n-Si wafers. According to an X-ray diffraction study, a strongly textured face-centered cubic structure was formed in the as-deposited films with an average grain sizes of about 10 - 70 nm. Experiments have demonstrated that the magnetic field and temperature dependences of the MR effect in Ni films shown two main peculiarities: (1) dependencies on the mutual orientations of vectors B, current and the film plane; (2) two contributions to the MR - negative anisotropic magnetoresistance and positive Lorentz-like MR

Gigantic Magnetoresistive Effect in n-SiSiO2Ni Nanostructures Fabricated by the Template-Assisted Electrochemical Deposition

The study of the carrier transport and magnetotransport in n-Si/SiO2/Ni nanostructures with granular Ni nanorods embedded into the pores in SiO2 was performed over the temperature range 2 – 300 K and at the magnetic field induction up to 8 T. In n-Si/SiO2/Ni nanostructures at temperatures of about 25 K a huge positive MR effect is observed. Possible mechanisms of the effect is discussed

Presence of inductivity in (CoFeZr)x(PZT)1-x nanocomposite produced by ion beam sputtering

This paper presents the investigations of the electrical properties of the (CoFeZr)x(PZT)1x nanocomposite with the metallic phase content x = 43:8 at.%, which was produced by ion beam sputtering. Such preparation took place under an argon atmosphere with low oxygen content with its partial pressure PO2 = 2 mPa. The measurements were performed using alternating current within the frequency range of 50 Hz – 0.1 MHz for measuring temperatures ranging from 238 K to 328 K. The (CoFeZr)43:8(PZT)56:2 nanocomposite sample subjected to a 15 min annealing process in air at the temperature Ta = 423 K demonstrates a phase angle of 90 in the frequency range 50 Hz – 0.1 MHz. It corresponds to the capacitive type of conduction. In the frequency range 10 – 100 kHz sharp minima in selected conductivity vs. frequency characteristics occur, which corresponds to a current resonance phenomenon in RLC circuits. In case of a sample annealed at Ta = 498 K the inductive type of conduction with +90 occurs in a high frequency area. At the frequency fr characterized by the phase angle = 0 , the capacity value reaches its local minimum. It indicates a voltage resonance phenomenon in conventional RLC circuits. The +90 crossing in the frequency dependence of phase angle corresponds to the current resonance phenomenon, which is represented by a strong local minimum in the conductivity vs. frequency characteristics

Percolation phenomena in Cux(SiOy)100-x nanocomposite films produced by ion beam-sputtering

In this paper the results of examinations of nanocomposites Cux(SiOy)100x produced by ion beam sputtering using argon ions were presented. The examinations were performed by the use of ac devices for measuring frequency in the range 50 Hz - 1 MHz and temperatures from 81 K to 273 K. The measurements were performed for the samples directly after production. Based on temperature dependences of conductivity , which were determined at the frequency 100 Hz, the Arrhenius graphs were prepared. From these graphs conductivity activation energies E were calculated. Dependences of conductivity and activation energy of electrons on the metallic phase content x at the frequency 100 Hz were determined. Analysis of the obtained dependences shows that conductivity is a parabolic function of the metallic phase content x in nanocomposites. Changes of activation energies of nanocomposites, in which metallic phase contents are in the ranges x < 12 at.% and x > 68 at.%, demonstrate negative values and metallic type of conductivity. In the range 12 at:% < x < 68 at:% activation energies have positive values and the dielectric type of conductivity. It was established that for the metallic phase content of about 68 at.% the real percolation threshold occurs, and the conduction changes from dielectric to metallic type

Electrical Properties of the Layered Single Crystals TlGaSe2 and TlInS2

In the doped crystals TlGaSe2 and TlInS2, using method of temperature dependencies of DC resistance in the temperature range of 100 – 300 K, the phase transitions at the temperatures of 240 – 245 K and 105 – 120 K were observed. The AC conductance measurements at room temperature indicated the hopping mechanism of carrier transport in the studied samples

Диагностика частотной области изоляции трансформатора

The first part of paper deals with the base information about diagnostics of power transformers. In this part are presented differently insulating methods, for example method of recovery voltage method, method of polarization and depolarization currents and chromatographic analysis.The second part of paper deals use of method of frequency domain spectroscopy for oil power transformers. This method is used in analysis insulating condition of power transformer with system of oil-paper. It was found, that the results of these tests are highly impacted by the operating temperature during the experimental measurement. Moisture and conductivity between insulating paper and oil in an insulating system are highly dependent from temperature.In the other part, the paper presents experimental results of the frequency diagnostic measurement for a real single-phase traction transformer 110/27 kV at different operating temperatures and states (with oil and without).Finally in the last part, the paper presents comparing frequency insulating measurements among several the same single-phase transformers 110/27 kV.В первой части статьи приведены базовые сведения о методах диагностики силовых трансформаторов. В этой части представлены различные методы исследования изоляции, в частности, метод восстановления напряжения, метод токов поляризации и деполяризации и метод хроматографического анализа.Во второй части статьи рассмотрено использование метода частотной спектроскопии для масляных силовых трансформаторов. Данный метод использован для анализа состояния изоляции силовых трансформаторов с системой масло-бумага. Определено, что на результаты такого анализа значительное влияние оказывает температура окружающей среды при проведении измерений. Влажность и проводимость между бумажной изоляцией и маслом существенно зависят от температуры.Далее в статье приведены экспериментальные результаты диагностических частотных измерений для однофазного тягового трансформатора 110/27 кВ при различных значениях температуры окружающей среды и в различных состояниях (с маслом и без масла).В завершающей части статьи выполнено сравнение результатов частотных измерений нескольких однотипных однофазных трансформаторов 110/27 кВ

Dielectric properties of nanocomposite (Cu)x(SiO2)(100-x) produced by ion-beam sputtering

It has been established that in the nanocomposite Cux(SiO2)(100 x) with the metallic phase content x = 27.27 at.% the following phenomena occur: hopping conductivity, additional polarity and coilless-like inductance. Coilless-like inductance phenomenon consists in the occurrence of positive values of phase shift in the high frequency area. Activation energy of the dielectric relaxation time for copper nanoparticles of unoxidized surface is of approx. 0.0003 eV, whereas surface oxidation causes a potential barrier occurrence and activation energy increase up to approx. 0.3360 eV. Comparative analysis of results obtained for the Cux(SiO2)(100 x) material and the measurements results obtained for the nanocomposites (FeCoZr)x(Al2O3)(100 x), (FeCoZr)x(CaF2)(100 x) and (FeCoZr)x(PZT)(100 x), which containing nanoparticles of ferromagnetic alloy, has been performed. It has shown that the type of magnetic properties of metallic phase, which is ferromagnetic ones for FeCoZr and diamagnetic ones for Cu, does not affect capacitive and inductive phenomena of the nanocomposites. The phenomena are related only to the nanogranular structure of the materials and the hopping mechanism of the charge transport between the metallic phase nanoparticles

Mechanisms of carrier transport in Cux(SiO2)1-x nanocomposites manufactured by ion-beam sputtering with Ar ions

The present paper investigates the temperature/frequency dependences of admittance Z in the granular Cux(SiO2)1x nanocomposite lms around the percolation threshold xC in the temperature range of 4 30 K and frequencies of 20 MHz. The behavior of low-frequency ReZ(T) dependences displayed the predominance of electrons hopping between the closest Cu-based nanoparticles for the samples below the percolation threshold xC = 0:59 and nearly metallic behaviour beyond the xC. The high-frequency curves ReZ(f) at temperatures T > 10 K for the samples with x < xC exhibited behavior close to ReZ(f) fs with s 1:0 which is very similar to the known Mott law for electron hopping mechanism. For the samples beyond the percolation threshold (x > xC), the frequency dependences of ReZ(f) displayed inductive-like (not capacitive) behaviour with positive values of the phase shift angles